Character design has been a guilty pleasure of mine since middle and high school. I absolutely love fabricating the intricate details of each character's history and personality. This skill has come in extremely useful in character and story creation for game design, and persona creation in user-centered design. But beyond even that, it's simply something I intuitively get, am good at, and love doing.
Three characters are showcased below. The groundwork of their backgrounds are set from the Kingdom Hearts video game, the Harry Potter novel, and the D.Grey-Man Japanese cartoon series, respectively (I claim no rights to any of these worlds or the original characters in them). Comprehensive character information can be found on my deviantART account.
Selixia, one of my oldest and easily most complex characters, is a Nobody. And I mean this in the nicest way possible-- the girl is from the world of Kingdom Hearts II. Anyone familiar with the PS2 game would remember that the main group of antagonists are "Nobodies," husks of their former selves, whose wills were strong enough to gained a consciousness in the absence of both soul and heart.
Selixia is quirky, witty, manipulative, and sadistic. Several versions of her have existed, for purposes of story-telling, and she generally has a nasty element under her control - usually illusions or sanity.
Your ally one minute, a despised enemy the next, the girl is a very much chaotic neutral character, and enjoys causing confusion and existential crises in the protagonists about good versus evil. She's quite good at what she does.
Magic aside, Tacey Flynn is perhaps my most human character (alas, I am a huge sucker for fantasy). Tacey hails from the world of Harry Potter.
She's a fifth-year Slytherin from a long line of Slytherins, and is pretty typical of the kind of person you'd expect in the Slytherin house - she's clever, ambitious, charismatic, and a pathological liar.
Tacey comes from a black sheep branch of a well-known Slytherin bloodline. Her father, disowned by her paternal grandfather, is obsessed with human technology, and is pushing hard for the legalization of integrating magic and technology. Tacey, although still hesitant of giving up her childhood dream of being an Auror, is the child her father wishes to follow in his footprints. She's trapped between the world of magic and the world of muggles (humans), especially on her father's insistence that she enroll in Oxford engineering during the summer.
This is Rinoa Lestrange, from the world of D.Grey-Man. She's an Exorcist, in possession of a special weapon that gets rid of demons that plague the world.
Most all Exorcists come from rather dark pasts (ones that usually drive them to accept the tough, violent life of an Exorcist), and Rin is no exception. Rin's history is shrouded in darkness and death, and as a result, she's become wild, battle-crazed, and quite inclined to angst. One of the most prominent themes in D.Grey-Man is Christianity, and the depiction of Exorcists as God's army. I thusly made her a Buddhist in her pre-Exorcist life to add to the angst.
The same character two years later. Because of her recklessness, she's had a rather unsuccessful battle with an enemy she had no chance of defeating. She's lost her voice, fine motor control in her fingers, and the ability to fight efficiently with her weapon. Despite this, Rinoa has matured quite a bit. She's become quite earnest although she still hasn't been able to let go of her grudge against her foes.